This invention relates to a pool ball having a spherical body of nonmetallic material and a metal insert in the form of a ring and to a method of making the pool ball such that the center of mass of the metal insert coincides with the geometric center of the pool ball.
Coin operated pool tables typically include passageways leading from each of the pockets to a locked compartment for retaining the pool balls as they are knocked into the pockets during the progress of a game. The compartment remains locked until a coin of proper denomination is deposited at which time the compartment opens to provide access to the pool balls therein. A cue ball for use in such coin operated pool tables must be separated from the object balls and prevented from entering the locked compartment in the event that the cue ball has been inadvertently scratched or knocked into one of the pockets during the progress of the game.
Known methods of separating cue balls include providing a cue ball which is of a different size or weight than the object balls, detecting the difference mechanically and preventing the cue ball from entering the locked compartment. This has been found unacceptable since it is desirable that the cue ball have the same physical characteristics as the object balls.
Another known method of separating the cue ball includes providing a cue ball having an insert of magnetic material located within the ball as near as possible to the surface thereof so that the cue ball may be directed into an unlocked compartment by means of a magnet. As shown in U.S. Pat. No. 3,738,655, the magnetic cue ball may be formed having a hollow sphere of magnetic material with a perforation therein. A plastic resin is poured into the hollow sphere through the perforation to form a core. The core is then encapsulated in a shell of the plastic resin to form the cue ball. Another method of making a magnetic cue ball includes molding plastic resin about a spherical cage formed of uniformly spaced steel strips. A magnetic cue ball may further be formed of a sphere of plastic resin having grooves therein. Strips of magnetic material are disposed within the grooves and the grooves filled with plastic resin to the outer surface of the ball.
Still another method of separating a cue ball is to provide an induction coil located about a central passageway of the pool table and through which all of the pool balls roll. Downstream of the induction coil, the central passageway branches off into a passageway leading to the locked compartment for object balls and a passageway leading to an unlocked compartment for the cue ball. When a cue ball having a metal insert therein rolls through the induction coil, the field produced by the coil is affected such that the output of the coil signals an electronic circuit which actuates a mechanical kicker or the like disposed in the central passageway near the point at which the passageway branches off. The kicker when actuated knocks the cue ball into the passageway leading to the unlocked compartment. Known cue balls for use with an induction coil separating system have been formed with a solid spherical core of metal such as aluminum or the like and about which a plastic resin is molded.
Numerous problems have arisen in manufacturing cue balls having metal inserts therein as described above. One of the most apparent problems arises in centering the insert within the cue ball to provide a balanced ball having a true roll. The known methods of centering a solid spherical metal insert or an insert in the form of a spherical cage are complex, costly and often inaccurate.
Further, where it is desired to provide a cue ball of approximately the same weight as the object balls, the density of the metal material forming the insert has been a crucial design factor in manufacturing known cue balls with metal inserts. Because large quantities of metal are used to form the inserts, the density of the metal must be approximately equal to the density of the plastic resin forming the remainder of the ball. Therefore, only a limited number of metals having an appropriate density could heretofore be used.